Part of Expression Blend (3?) ... saw in the Keynote, looks good for rapid prototyping of conceptual UI. But isn't that kinda what xaml and Expression were supposed to be about already?

Deliberately sketchy hand-drawn graphics to avoid users getting too wrapped up in the polish, rather than features. It changes the quality of the feedback!

Loving the app flow setup step at the start. Nicely informal yet fully descriptive. Design time notes... real controls under-the-hood. Seems like with a trained operator it could be an ideal solution to sit down with the end-user with.

Possible to import actual UI sketches or use a tablet. You can actually link actions and transitions to parts of your sketch! You can actually *draw* edit controls or buttons!

I am sure that he was going to go into a lot more detail about the features of Sketchflow; probably data binding, transitions, etc... but I think I am already sold personally. Will have to find out how much it'd cost.